Screening for diseases with molecular defects in protein C receptor

内皮细胞蛋白C受体(EPCR)能高亲和力结合血浆抗凝蛋白C，蛋白C以丝氨酸蛋白酶的酶原形式循环，在内皮细胞表面转化为活性酶时起抗凝剂的作用。凝血酶/血栓调节蛋白(TM)复合体被发现介导了激活的催化反应。我们发现，利用转染的细胞系和功能封闭的抗EPCR单抗，EPCR大大加速了该复合体介导的蛋白C的激活。EPCR在生理条件下对蛋白C的激活似乎是必不可少的，因此，该分子的功能或表达异常可能会导致凝血功能的缺陷。我们发现，在从胶质母细胞瘤和单核细胞白血病患者建立的几个细胞系中，都能诱导出功能性的EPCR。M4型和M5型急性粒细胞白血病患者外周血单个核细胞(PBMC)也呈EPCR阳性，而健康献血员的PBMC则呈阴性。EPCR可能是某些类型癌症的一个新的标志物，该分子的异常表达可能解释了癌症中某些凝血功能的紊乱。我们还建立了检测EPCR基因缺陷的筛查系统，建立了扩增EPCR外显子的聚合酶链式反应方法，并建立了直接测序方法。使用这些方法进行筛查现在正在进行中。

The endothelial cell protein C receptor (EPCR) is capable of high-affinity binding specific for plasma anticoagulant protein C.Protein C circulates as a zymogen form of serine protease and functions as an anticoagulant when is converted to active form of enzyme on the endothelial cell surface. The thrombin/thrombomodulin (TM) complex has been found to mediate the catalytic reaction for the activation. We found that EPCR greatly accelerated protein C activation mediated by the complex by using transfected cell lines and function blocking anti-EPCR monoclonal antibodies. EPCR appears to be essential for protein C activation under the physiological conditions, therefore, abnormal function or expression of this molecule might cause defects in blood coagulation. We found that functional EPCR was induced in several cell lines established from glioblastoma and monoblastic leukemia patients. Peripheral blood mononuclear cells (PBMC) from patients with acute myerocytic leukemia type M4 and M5 were also positive for EPCR.In contrast, PBMC from healthy donors were negative for the antigen. EPCR could be a novel marker for some types of cancers, and abnormal expression of this molecule might explain some disorder of blood coagulation in cancer. We also developed a screening system to detect the genetic defects of EPCR.We established PCR methods to amplify the exons of EPCR and also established direct sequencing methods. Screening by using these methods is now under going.